Typically, snowmobiles have two front skis connected to a handlebar and a rear endless track connected to an engine to propel the snowmobile. In such typical snowmobiles, the snowmobile is steered by turning the handlebar in the direction in which the driver wants to turn. This is known as steer-in-direction. During a turn, the suspension assembly connected to the ski on the outside of the turn is compressed, causing the snowmobile to roll slightly toward the outside of the turn, which the driver can compensate by leaning toward the inside of the turn.
In other vehicles, such as motorcycles, the vehicle is steered by what is known as countersteering. In a motorcycle for example, the motorcycle turns by leaning in the direction of the turn. To achieve this leaning, the driver momentarily turns the handlebar in the direction opposite to the direction of the turn (i.e. the driver countersteers).
Driving a vehicle that can lean into a turn offers a much different driving experience than driving a vehicle that is steer-in-direction. It would be desirable to at least some drivers to have the driving experience of a leaning vehicle on a vehicle having three ground engaging members such as a snowmobile.
U.S. Pat. No. 7,648,148 B1, issued Jan. 19, 2010, and U.S. Pat. No. 7,530,419 B2, issued May 12, 2009, describe three-wheel vehicles that can lean in a turn. In vehicles of this type, the frame of the vehicle is pivotally connected to a shock tower (also known as a transfer frame) and the front shock absorbers associated with the two front wheels are connected at their upper end to the shock tower. During a turn, the frame pivots into the turn like on a motorcycle, but the shock tower remains essentially vertical. As a result, the front shock absorbers do not get compressed due to the leaning of the frame.
In certain conditions, however, operating the vehicle could be complicated by the relative lean between the shock tower and the frame. When traveling along a slope, traveling on areas of low adherence such as ice, or traversing rough terrain at low speeds, leaning could negatively influence the user's control of the vehicle. Further, any such condition may appear when the vehicle is in motion or already leaning away from vertical. For example, when traveling along a slope, the frame of the vehicle could lean toward the downhill side of the slope and increase the possibility of the vehicle tipping over.